Steering shaft lock actuator

ABSTRACT

A steering shaft lock actuator may include a motor having an output shaft, a drive train, and a lost motion device. The drive train may be coupled to the output shaft and may linearly urge a locking member to an unlocked position when the motor is energized. The lost motion device may be configured to store energy when the locking member is in the unlocked position and utilize the stored energy to drive the locking member toward a locked position with a steering shaft when the motor is de-energized.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Application Ser. No. 60/608,261, filed Sep. 9, 2004, theteachings of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to steering shaft lock actuators.

BACKGROUND

In the automotive industry, it is desirable to lock the steering shaftof a vehicle in place to prevent rotation of the steering shaft when thevehicle is not in use. Known systems utilize a keyed ignition systemassociated with the steering column. When the key is removed from theignition, a steering shaft lock mechanism may be actuated to lock thesteering shaft in place. Other vehicles utilize a keyless system or asystem where the keyed ignition system is not associated with steeringcolumn. For these configurations, a separate actuator may be used tolock and unlock the steering shaft.

In one known steering shaft lock actuator, a locking member may be movedby the actuator from an unlocked to a locked position. When in thelocked position, the locking member may engage a recess in the steeringshaft to lock the steering shaft. The recess may be formed by adjacentteeth of a toothed ring that may be coupled to the steering shaft. Anobstruction, e.g., a tooth of the toothed ring, may be encountered asthe actuator attempts to drive the locking member to the lockedposition. The actuator motor may remain energized so that the motordrives the locking member to the locked position when the obstruction isremoved. This can stress the motor and lead to early failure of theactuator. Actuator failure may be manifested in a failure of to lock thesteering shaft when the vehicle is not in use and/or inadvertent lockingof the steering shaft during normal driving conditions, which, ofcourse, would pose a critical safety hazard.

Accordingly, there is a need in the art for a steering shaft lockactuator configured to protect the actuator if an obstruction isencountered when the actuator attempts to drive the locking membertoward a locked position and there is a need for a reliable steeringshaft lock actuator to protect against inadvertent locking of thesteering shaft during normal driving conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiments of the disclosed subject matterwill become apparent as the following Detailed Description proceeds, andupon reference to the Drawings, where like numerals depict like parts,and in which:

FIG. 1A is a block diagram of a steering shaft lock actuator in anunlocked position with its locking member retracted;

FIG. 1B is a block diagram of the steering shaft lock actuator in acocked position;

FIG. 1C is a block diagram of the steering shaft lock actuator in alocked position with its locking member fully extended once theobstruction of FIG. 1B is removed;

FIG. 2 diagrammatically illustrates a first embodiment of a steeringshaft lock actuator consistent with the present invention;

FIG. 3 is plan view of the locking member and locking arm of FIG. 2;

FIG. 4A is a plan view of the locking member and eccentric cam of FIG. 2in an unlocked position with the locking member retracted;

FIG. 4B is a plan view of the locking member and eccentric cam of FIG. 2in a cocked position with the locking member blocked by an obstruction;

FIG. 4C is a plan view of the locking member and eccentric cam of FIG. 2in a locked position with the locking member extended;

FIG. 5A diagrammatically illustrates a second embodiment of a steeringshaft lock actuator consistent with the present invention in an unlockedposition with the locking member retracted;

FIG. 5B diagrammatically illustrates the second embodiment of a steeringshaft lock actuator consistent with the present invention in a lockedposition with the locking member extended; and

FIG. 6 is an electrical block diagram that may be utilized to controlthe steering shaft lock actuator of the first and second embodiments.

Although the following Detailed Description will proceed with referencebeing made to illustrative embodiments, many alternatives,modifications, and variations thereof will be apparent to those skilledin the art. Accordingly, it is intended that the claimed subject matterbe viewed broadly.

DETAILED DESCRIPTION

The description provided herein is with reference to various exemplaryembodiments. It is to be understood that the embodiments describedherein are presented by way of illustration, not of limitation. Thepresent invention may be incorporated into a wide variety of systemswithout departing from the spirit and scope of the invention.

Turning now to FIGS. 1A-1C, there is shown in block diagram form anexemplary steering shaft lock actuator 102 consistent with the inventionin an unlocked position (FIG. 1A), a cocked position (FIG. 1B), and alocked position (FIG. 1C.) The steering shaft actuator 102 may include alocking member 108 coupled to a motor through a gear train for extendingand retracting the locking member to lock and unlock a steering shaft110. A toothed ring 140 may be affixed to the shaft about thecircumference of the shaft. For clarity of illustration, only a portionof the toothed ring 140 having teeth 142 and 140 is illustrated.

FIG. 1A illustrates the steering shaft lock actuator 102 in an unlockedposition with the locking member retracted away from the toothed ring140. In the unlocked position, the steering shaft 110 is free to rotate,unencumbered by the locking member 108. FIG. 1B illustrates the steeringlock actuator 102 in a cocked position wherein the locking member 108 isextended toward the toothed ring but has been blocked from entering arecess 143 between adjacent teeth by an obstruction. In one example, theobstruction may occur when the locking member 108 and the teeth of thetoothed ring 140 are not properly aligned so that the locking member 108contacts one of the teeth, e.g., tooth 142, as it attempts to extendinto the recess 143.

Advantageously, the steering lock actuator 102 may include a lost motiondevice, e.g., a compression spring in one embodiment, having sufficientstored energy in the cocked position to drive the locking member 108once the obstruction is removed. Thus, the actuator and a motor thereinmay be de-energized when the locking member 108 is in the cockedposition. For instance, as the steering shaft 110 is rotatedcounterclockwise from its position illustrated in FIG. 1B to itsposition illustrated in FIG. 1C, the lost motion device may force thelocking member 108 to fully extend to a locked position into the recess143 between teeth 142 and 144 of the toothed ring 140.

FIG. 2 diagrammatically illustrates one exemplary embodiment 102 a of asteering shaft lock actuator consistent with the present invention. Thesteering shaft lock actuator 102 a may be configured to urge the lockingmember 108 a linearly in the directions indicated by arrows 260 tounlocked, cocked, and locked positions, e.g. as illustrated in FIGS.1A-1C. The steering shaft actuator 102 a may include a housing 202configured to mate with a cover 204 to protect components of theactuator 102 a. A collar 207 may be affixed to the housing 202 and maybe affixed proximate a steering shaft. The collar 207 may have anopening 233 to permit linear travel of the locking member 108 atherethrough.

The steering shaft lock actuator 102 a may further include a motor 212having an output shaft 213, a drive train coupled to the output shaft,and a lost motion device, e.g. a compression spring 232. The drive traincoupled to the output shaft 213 may include a worm gear 203 and a wormwheel 240 including an eccentric cam 250. The steering shaft lockactuator 102 a may further include the locking member 108 a, a lockinglever 210, a solenoid 214, a printed circuit board (PCB) assembly 205,magnets 246 and 206, and position sensors 242, 244. The locking member108 a may have a first opening 270 and a second opening 272. The motor212 may be a permanent magnet DC motor. The PCB assembly 205 may includea plurality of contacts 209 that extend into an opening 211 of the cover204 to form a plug connection for an associated plug. The plugconnection may provide connection to a power source and a centralcontroller of the vehicle.

In general, the rotary motion provided by the motor 212 may providelinear motion to the locking member 108 a to linearly drive the lockingmember in the direction of arrows 260. A drive gear, e.g., the wormwheel 240 having the eccentric cam 250, may linearly urge the lockingmember 108 a to the desired locked or unlocked position. The compressionspring 232 may be positioned to bias the locking member 108 a toward afully extended or locked position. The compression spring 232 may haveone end positioned against a tab 256 of the housing 202 and an oppositeend positioned against an edge 271 of the first opening 270 of thelocking member 108 a (see also FIG. 3). The position of the lockinglever 210 and also the eccentric cam 250 may prevent extension of thelocking member 108 a under the bias of the compression spring 232. Thelocking lever 210 may therefore provide a safety feature to prevent aninadvertent extension of the locking member 108 a.

The locking lever 210 may include a longitudinal extension 280, alocking arm 226 extending from one end of the longitudinal extension280, and a projection 224 extending from the other end of thelongitudinal extension 280. The locking arm 226 may have an opening 230to accept a shaft 274. The projection 224 of the locking lever 210 mayhave an opening configured to mate with a plunger 218 of the solenoid214. The locking lever 210 may have a locked an unlocked position. Whenin the locked position, the locking lever 210 may prevent axialextension of the locking member 108 a to an extended or locked position.When in the unlocked position, the locking lever 210 may enable thelocking member 108 a to extend to a locked position.

FIG. 3 is a plan view of the locking arm 226 of the locking lever 210with the locking arm 226 shown in phantom in a locked position 226′ andunlocked position 226″. To drive the locking arm 226 to its lockedposition 226′, the solenoid 226 may be de-energized. When the solenoidis de-energized, the compression spring 220 about the plunger 218 of thesolenoid 214 may urge the projection 224 of the locking lever 210 awayfrom the solenoid so that a portion of the locking lever 210 is urgedinto a slot 234 of the locking member 108 a. The portion of the lockinglever 210 urged into a slot 234 may be the longitudinal extension 280 ofthe locking lever 210. When in a locked position, as illustrated in FIG.2 and the position 226′ of FIG. 3, the locking member 108 a may beprevented from linearly extending toward its locked position.

To drive the locking arm 226 to its unlocked position 226″, the solenoidmay be energized to pull the plunger 218 against the biasing force ofthe compression spring 220. The plunger 218 may include a lip 216 thatpulls the projection 224 of the locking lever 210 and hence the lockingarm 226 may be rotated counterclockwise to its unlocked position 226″.When in the unlocked position 226″, the locking lever 210 is no longerin the notch 234 and may allow linear extension of the locking member108 a toward its locked position.

FIGS. 4A-4C are plan views of the locking member 108 a, eccentric cam250 of the worm wheel 240, and locking arm 226 of the locking lever 210in unlocked (FIG. 4A), cocked (FIG. 4B), and locked (FIG. 4C) positionsto further illustrate operation of the steering shaft lock actuator 102a of FIG. 2. The motor 212 may drive the worm gear 203 which may bemeshingly engaged with a portion of the worm wheel 240. As the wormwheel rotates, the eccentric cam 250 may contact a portion of the secondopening 272 in the locking member 108 a to linearly urge the lockingmember 108 a in the direction indicated by arrow 402 to a retracted orunlocked position of FIG. 4A. The locking arm 226 of the locking lever210 may also be urged into a locked position within the slot 234. Thecompression spring 232 may be compressed between the locking member 108a and the tab 256 of the housing 202 when the locking member is urged toits unlocked position. The compression spring 232 may be sufficientlycompressed to store enough energy to later drive the locking member 108a toward its locked position.

As shown in FIG. 4B, the motor 212 may drive the worm wheel 240 so thatthe eccentric cam 250 is rotated counterclockwise creating space 483 forthe compression spring 232 to drive the locking member 108 a linearlyoutward in the direction indicated by arrow 403. The locking arm 226 mayalso be driven to its unlocked position to enable extension of thelocking member 108 a. However, an obstruction may be encountered by thelocking member 108 a as its attempts to fully extend. Advantageously,the actuator 102 a may maintain the cocked position of FIG. 4B until theobstruction is removed. While in this cocked position, the actuator 102a may be de-energized and hence the motor 212 may also be de-energized.The compression spring 232 may be sufficiently compressed in theposition of FIG. 4B with enough stored energy to drive the lockingmember 108 a linearly outward once the obstruction is removed.

FIG. 4C illustrates the locking member 108 a fully extended to itslocked position by the stored energy of the compression spring 232 oncethe obstruction encountered in FIG. 4B is removed. Compared to FIG. 4B,the compression spring 232 has driven the locking member 108 to a fullyextended position until a portion of the second opening 272 of thelocking member 108 a contacts the eccentric cam 250. Hence, the size ofthe eccentric cam 250, the placement of the opening 230 for the shaft274 in the eccentric cam, the amount of rotation of the worm wheel 240,and the length of the compression spring 232 may control the lineartravel distance of the locking member 108 a from its unlocked to itsfully extended locked position.

The steering shaft lock actuator 102 a may also provide positionalfeedback for at least one element of the actuator 102 a. For instance,the position of the eccentric cam 250 of the worm wheel 240 may bemonitored. To accomplish this, one or more magnets, e.g., magnet 246,may be coupled directly or indirectly to the worm wheel 240. One or moremagnetic sensors may be positioned proximate the rotating worm wheel240. In one embodiment, the magnetic sensors may be Hall Effect sensors.Hall Effect sensors 242 and 244 may be positioned 180 degrees apart fromeach other about the shaft 274 on the PCB assembly 250. As the positionof the worm wheel 240 and hence the eccentric cam 250 varies, themagnetic field sensed by the Hall Effect sensors 242 and 244 may varybased on proximity of the magnet 246 relative to each of the Hall Effectsensors 242 and 244. Accordingly, the position of the eccentric cam 250may be ascertained from the magnetic field sensed by the Hall Effectsensors 242 and 244. Hall Effect sensors may provide for reliability andrepeatability of positing sensing over voltage and temperature extremes.In addition to, or in lieu of, magnetic field sensors, a contact type ofsensor or switch may be utilized to provide position feedbackinformation on the position of the eccentric cam 250.

In addition to, or in lieu of, sensing the position of the eccentric cam250, the actuator 102 a may sense the position of the locking lever 210to determine if it is in its locked or unlocked position. A magnet 206and another Hall Effect sensor may be utilized to determine the positionof the locking lever 210. Similarly, a contact type of sensor switch maybe utilized to provide position feedback information regarding theposition of the locking lever 210.

FIGS. 5A and 5B diagrammatically illustrate another exemplary embodiment102 b of a steering shaft lock actuator consistent with the presentinvention in an unlocked and locked position, respectively. Compared tothe steering shaft actuator 102 a of the first embodiment, the drivegear of the drive train may include an elliptical spur gear 515 asopposed to the worm wheel 240 with the eccentric cam 250. The drivetrain may further a spur gear 540 in meshing engagement with theelliptical spur gear 515. The elliptical spur gear arrangement incooperation with the compression spring 532 may translate rotary motionof the motor 512 to linear output motion of the locking member 108 b.Other components and operation of the steering shaft lock actuator 102 bmay be consistent with the first embodiment of the steering shaftactuator 102 a. For example, the steering shaft actuator 102 b may alsoprovide positional feedback and a locking lever arrangement.

FIG. 5A diagrammatically illustrates the steering shaft lock actuator102 b in an unlocked position with the locking member 108 b retracted.The motor 512 may drive the drive train including the spur gear 540 andthe elliptical spur gear 515 so that a portion of the elliptical spurgear 515 contacts the locking member 108 b and drives it to theretracted position. The compression spring 532 may therefore becompressed in the unlocked position between the tab 546 and a portion ofthe locking member 108 b. The compression spring 532 may be compressedsufficiently to have enough stored energy to later drive the lockingmember 108 b toward a locked position when permitted by the movement ofthe elliptical spur gear 515.

FIG. 5B diagrammatically illustrates the steering shaft lock actuator102 b in a locked position with the locking member 108 b extended. Themotor 512 may drive the gear train including the spur gear 540 andelliptical spur gear 515 so that the elliptical spur gear is rotatedfrom its position in FIG. 5A to its position in FIG. 5B to enable thecompression spring 532 to drive locking member 108 b toward the lockedposition. If the locking member 108 b encounters an obstruction, thelocking member 108 b may remain in a cocked position and the actuatormay de-energize the motor 512. Once the obstruction is removed, thecompression spring 532 may drive the locking member 108 b into itslocked position.

FIG. 6 is an electrical block diagram 600 that may be utilized tocontrol the steering shaft lock actuator of the first and secondembodiments. A controller 604 may accept a variety of input signals andcontrol the motor 612, e.g., motor 212 of the first embodiment or motor512 of the second embodiment, to thereby control the position of thelocking member 108. The controller 604 may also control the solenoid614, e.g., solenoid 214 of the first embodiment, to thereby control theposition of the lock lever 210. In one embodiment, the controller 604may be a microcontroller.

One or more position sensors 608 may provide a signal to the controller604 representative of the position of a drive gear of the drive traindriven by the motor. For instance, the drive gear may be the worm wheel240 having the eccentric cam 250 in the first embodiment and the drivegear may be the elliptical spur gear 215 in the second embodiment.Another position sensor 610 may provide a signal to the controller 604representative of the position of the lock lever 210. The controller 604may also store and retrieve information from memory 606. A power supply602 may provide power for the controller 604 and may also providededicated I/O lines from discrete vehicle inputs communicated to theactuator via a serial data bus (e.g., a LIN, CAN or J1850 bus). Otherinputs may also be provided to the controller 604, e.g., a user commandto drive the locking member toward the locked position may also bereceived by the controller 604.

In response to the various input signals and monitored conditions, thecontroller 604 may provide a signal to the motor 612 to drive thelocking member 108 to an unlocked or retracted position. The motor 612may accomplish this by driving a drive gear of the drive train coupledto an output shaft of the motor. The drive gear may contact the lockingmember and urge the locking member to its unlocked position. Thecontroller 604 may also instruct the motor to move the drive gear of thedrive train to enable the lost motion device, e.g., the compressionspring 232 of the first embodiment or compression spring 532 of thesecond embodiment, to drive the locking member toward a locked positionwith a steering shaft.

The steering shaft lock actuator may also drive the locking membertoward a locked position upon receipt of a command by a user. Theactuator may also include a safety mechanism that may prevent thelocking member 108 from engaging unless one or more logic criteria aremet in the electronics or software associated with the actuator orembedded in the controller 604.

Consistent with one aspect, the PCB layout and/or circuit design may bedesigned to minimize and/or mitigate inadvertent or unexpected operationof the actuator, which may, for example, be due to high levels ofelectromagnetic noise. The actuator may also be designed to haveintegral protection for the motor to prevent over heating and/or otherfailures. An actuator according to the present disclosure may includeintegrated control circuitry that may eliminate the need for an externalcontroller.

The drive train of an actuator according to the present disclosure mayprovided in numerous configurations. According to the first embodiment,the gear mechanism may use a worm gear and eccentric cam to translaterotary input from a motor to a linear output motion. According to thesecond embodiment, a worm gear may be attached to an elliptical spurgear. The eliptical spur gear may translate rotary input motion from themotor/upstream drive train to linear output motion. Other arrangementsmay be provided, for example including a worm gear with eccentric pinconnected to a drive linkage similar in funtion to that of a steamlocomotive, etc.

In summary, there is provided a steering shaft lock actuator. Thesteering shaft lock actuator may include a motor having an output shaft,a drive train, and a lost motion device. The drive train may be coupledto the output shaft, and may be configured to linearly urge a lockingmember to an unlocked position upon energization of the motor. The lostmotion device may be configured to store energy when the drive gearurges the locking member to the unlocked position and drive the lockingmember toward a locked position with a steering shaft when the motor isde-energized.

There is also provided a method including urging a locking member of asteering shaft lock actuator in a linear direction to an unlockedposition; storing energy in a lost motion device when the locking memberis urged to the unlocked position; and utilizing the stored energy todrive the locking member toward a locked position with a steering shaft.

There is also provided a system. The system may include a steeringshaft; and a steering shaft lock actuator configured to lock and unlockthe steering shaft. The steering shaft lock actuator may include a motorhaving an output shaft, a drive train, and a lost motion device. Thedrive train may be coupled to the output shaft, and may be configured tolinearly urge a locking member to an unlocked position upon energizationof the motor. The lost motion device may be configured to store energywhen the drive gear urges the locking member to the unlocked positionand drive the locking member toward a locked position with the steeringshaft when the motor is de-energized.

Advantageously, the motor of the actuator may be de-energized if anobstruction is encountered by the locking member when it is driventoward a locked position. This protects the motor from such blockedconditions and a lost motion device may have sufficient stored energy todrive the locking member to the locked position once the obstruction isremoved. In addition, various safety features such as a locking leverthat locks the locking member in its unlocked position further ensurethat the locking member may not be inadvertently locked during normaldriving conditions.

The terms and expressions which have been employed herein are used asterms of description and not of limitation, and there is no intention,in the use of such terms and expressions, of excluding any equivalentsof the features shown and described (or portions thereof), and it isrecognized that various modifications are possible within the scope ofthe claims. Other modifications, variations, and alternatives are alsopossible. Accordingly, the claims are intended to cover all suchequivalents.

1. A steering shaft lock actuator comprising: a motor having an outputshaft; a drive train coupled to said output shaft, said drive trainconfigured to linearly urge a locking member to an unlocked positionupon energization of said motor; and a lost motion device configured tostore energy when said locking member is in said unlocked position anddrive said locking member toward a locked position with a steering shaftwhen said motor is de-energized.
 2. The steering shaft lock actuator ofclaim 1, wherein said lost motion device comprises a compression spring.3. The steering shaft lock actuator of claim 2, wherein said lockingmember further has a cocked position when said locking member encountersan obstruction, and wherein said compression spring is configured todrive said locking member into said locked position when saidobstruction is removed.
 4. The steering shaft lock actuator of claim 1,wherein said drive train comprises a worm wheel having an eccentric cam,said eccentric cam contacting at least a portion of said locking memberto linearly urge said locking member to said unlocked position, andwherein said eccentric cam is configured to move to enable said lostmotion device to drive said locking member toward said locked position.5. The steering shaft lock actuator of claim 1, wherein said drive traincomprises an elliptical spur gear, said elliptical spur gear contactingat least a portion of said locking member to linearly urge said lockingmember to said unlocked position, and wherein said elliptical spur gearis configured to move to enable said lost motion device to drive saidlocking member toward said locked position.
 6. The steering shaft lockactuator of claim 1, further comprising a locking lever configured toengage said locking member to lock said locking member in said unlockedposition.
 7. The steering shaft lock actuator of claim 6, furthercomprising a solenoid having a plunger and a compression spring aboutsaid plunger, wherein said compression spring is configured to drivesaid locking lever to engage a portion of said locking member when saidsolenoid is de-energized, and wherein said locking lever is pulled bysaid plunger to disengage from said portion of said locking lever whensaid solenoid is energized.
 8. A method comprising: urging a lockingmember of a steering shaft lock actuator in a linear direction to anunlocked position; storing energy in a lost motion device when saidlocking member is urged to said unlocked position; and utilizing saidstored energy to drive said locking member toward a locked position witha steering shaft.
 9. The method of claim 8, wherein said lost motiondevice comprises a compression spring.
 10. The method of claim 9,wherein said locking member has a cocked position when said lockingmember encounters an obstruction, said method further comprisingde-energizing a motor of said steering shaft lock actuator when saidlocking member is in said cocked position.
 11. The method of claim 8,further comprising mechanically locking said locking member in saidunlocked position to prevent an inadvertent driving of said lockingmember toward said locked position.
 12. The method of claim 11, furthercomprising mechanically unlocking said locking member upon a usercommand to lock said locking member.
 13. A system comprising: a steeringshaft; and a steering shaft lock actuator configured to lock and unlocksaid steering shaft, said steering lock actuator comprising: a motorhaving an output shaft; a drive train coupled to said output shaft, saiddrive train configured to linearly urge a locking member to an unlockedposition upon energization of said motor; and a lost motion deviceconfigured to store energy when said locking member is in said unlockedposition and drive said locking member toward a locked position withsaid steering shaft when said motor is de-energized.
 14. The system ofclaim 13, wherein said lost motion device comprises a compressionspring.
 15. The system of claim 14, wherein said locking member furtherhas a cocked position when said locking member encounters anobstruction, and wherein said compression spring is configured to drivesaid locking member into said locked position when said obstruction isremoved.
 16. The system of claim 13, wherein said drive train comprisesa worm wheel having an eccentric cam, said eccentric cam contacting atleast a portion of said locking member to linearly urge said lockingmember to said unlocked position, and wherein said eccentric cam isconfigured to move to enable said lost motion device to drive saidlocking member toward said locked position.
 17. The system of claim 13,wherein said drive train comprises an elliptical spur gear, saidelliptical spur gear contacting at least a portion of said lockingmember to linearly urge said locking member to said unlocked position,and wherein said elliptical spur gear is configured to move to enablesaid lost motion device to drive said locking member toward said lockedposition.
 18. The system of claim 13, further comprising a locking leverconfigured to engage said locking member to lock said locking member insaid unlocked position.
 19. The system of claim 19, further comprising asolenoid having a plunger and a compression spring about said plunger,wherein said compression spring is configured to drive said lockinglever to engage a portion of said locking member when said solenoid isde-energized, and wherein said locking lever is pulled by said plungerto disengage from said portion of said locking lever when said solenoidis energized.